Nicotinamide adenine dinucleotide — a central coenzyme in cellular energy metabolism. Naturally declines with age. Parenteral administration bypasses first-pass metabolism for direct plasma elevation.
NAD+ (nicotinamide adenine dinucleotide) is a dinucleotide coenzyme with a molecular weight of 663.4 Da. It is present in every cell of the body and participates in over 500 enzymatic reactions — making it one of the most metabolically important molecules in human biology.
As a coenzyme, NAD+ functions as an electron carrier in redox reactions, shuttling electrons between metabolic pathways. It exists in two forms: NAD+ (oxidized, the electron acceptor) and NADH (reduced, the electron donor). The NAD+/NADH ratio is a key indicator of cellular metabolic state, influencing everything from glycolysis and the citric acid cycle to oxidative phosphorylation in the mitochondria.
Intracellular NAD+ levels decline with age — studies suggest roughly a 50% reduction between ages 20 and 60. This decline is attributed to increased consumption by enzymes such as CD38, PARP1 (poly ADP-ribose polymerase), and the sirtuins (SIRT1-7), combined with reduced efficiency of NAD+ biosynthesis pathways. Subcutaneous NAD+ injection is one approach to directly elevate plasma NAD+ levels, bypassing the oral bioavailability challenges of the molecule and its precursors.
NAD+ serves as a substrate and coenzyme across three major pathway families in human cells:
NAD+ accepts electrons during glycolysis and the TCA cycle, becoming NADH. NADH then donates those electrons to the mitochondrial electron transport chain to drive ATP synthesis. This is the fundamental energy currency pathway of the cell. Higher NAD+ availability supports more efficient ATP production.
The sirtuin family (SIRT1-7) are NAD+-dependent deacetylases that regulate gene expression, DNA repair, inflammation, and mitochondrial biogenesis. Sirtuins consume NAD+ as a co-substrate — they cleave NAD+ during the deacetylation reaction. Higher NAD+ availability supports greater sirtuin activity.
PARP1 and PARP2 are DNA repair enzymes that consume NAD+ to build poly-ADP-ribose chains at sites of DNA damage. Under conditions of accumulated DNA damage (aging, oxidative stress), PARP activity increases dramatically, depleting the cellular NAD+ pool. Exogenous NAD+ replenishment supports the DNA repair substrate pool.
Exogenous NAD+ administered subcutaneously enters the bloodstream rapidly, with peak plasma concentrations reached in approximately 30 minutes. The plasma half-life is short — roughly 45 minutes — reflecting rapid cellular uptake and enzymatic metabolism. However, the functional effects extend beyond plasma clearance as NAD+ is incorporated into intracellular metabolic pools.
| Parameter | Value |
|---|---|
| Plasma Half-Life | ~45 minutes |
| Time to Peak (Tmax) | ~30 minutes post-injection |
| Bioavailability (SubQ) | ~95% |
| Functional Duration | ~4 hours |
| Steady State (Daily Dosing) | Not applicable (cleared between daily doses) |
| Primary Clearance | Cellular uptake + enzymatic metabolism |
| Active Metabolites | NMN, NR, nicotinamide (all NAD+ pathway intermediates) |
NAD+ does not accumulate in plasma between daily doses — each injection produces a transient spike followed by rapid cellular uptake and clearance. This means there is no "steady state" in the traditional pharmacokinetic sense. Instead, the benefit model is cumulative: regular daily dosing replenishes intracellular NAD+ pools over time, supporting sustained metabolic function even though plasma levels return to baseline between doses.
Intravenous NAD+ infusions (250–750 mg over 2–4 hours) produce higher peak plasma levels but require clinical administration. Subcutaneous injection (50–250 mg) is self-administered and produces a more gradual absorption curve. Both routes bypass the gastrointestinal tract, which is the primary barrier to oral NAD+ bioavailability. Many longevity-focused protocols favor SubQ for the convenience of daily self-administration.
NAD+ dosing varies significantly between subcutaneous self-administration and clinical IV infusions. Commonly reported protocol structures:
Many NAD+ protocols favor morning administration. NAD+ plays a role in circadian rhythm regulation through sirtuin-mediated clock gene expression. Morning dosing aligns the transient NAD+ elevation with the body's natural metabolic upswing, when energy demands are highest and NAD+-dependent pathways are most active.
NAD+ for subcutaneous injection typically comes as a lyophilized powder or pre-mixed sterile solution. If using lyophilized vials, reconstitution is straightforward:
NAD+ lyophilized vial (commonly 100 mg, 250 mg, or 500 mg), sterile bacteriostatic water, alcohol swabs, and insulin syringes (29–31 gauge).
Swab the rubber stopper of both the NAD+ vial and BAC water vial with alcohol pads. Allow to air dry briefly.
For a 500 mg vial, adding 2 mL of BAC water produces a concentration of 250 mg/mL. Adjust volume based on your target concentration and vial size. Direct the stream against the glass wall, not onto the powder.
NAD+ dissolves readily — gentle swirling for 30–60 seconds is usually sufficient. The solution should be clear to slightly yellow. Do not use if cloudy or discolored.
For a 100 mg dose from a 250 mg/mL solution, draw 0.4 mL (40 units). Inject subcutaneously in the abdomen or thigh. Rotate injection sites.
Refrigerate reconstituted NAD+ at 2–8°C. Most protocols recommend use within 28 days. NAD+ is sensitive to light and heat — avoid leaving vials at room temperature for extended periods.